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GPS
The position calculation procedure is indicated in the following three steps:
1. GPS satellites continuously transmit their own precise orbital data and the GPS receiver com
putes their locations by receiving this data.
2. In this receiving process, the GPS receiver measures very accurate distances to the satellites,
using the "Spread Spectrum Modulation" method. Excellence in GPS's position-fixing accuracy i
s mainly due to this technology.
3. When the satellite locations and their distances are known, the GPS receiver fixes its own p
osition by triangulation:
[The GPS position calculation]
As illustrated in the previous figure, the position is calculated as the meeting point of three
spheres which are drawn around the three satellites with diameters d1, d2 and d3.
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